In general, various touch switches being operated by sensing a variation in capacitance have been known.
For example, as illustrated in (A) and (B) of FIG. 1, as a representative touch switch, there is Korean Patent Laid-Open Publication No. 10-2011-0094568 “a capacitance-sensitive touch switch” (hereinafter referred to as the “switch”) which had been filed by the present applicant and was then published, and the contents thereof are as follows.
Referring to the drawings illustrated, a conventional switch 10 includes an upper substrate 11, a lower substrate 12, a sensor electrode 13, an electrode pad 14, a current-carrying member 15, and a capacitance sensing circuit 16.
The upper substrate 11 is made of a non-conductive material, a surface thereof which comes into direct and indirect contact with the human body is formed in a curved surface, and the conductive sensor electrode 13 is provided in an inner side thereof.
The lower substrate 12 is a printed circuit board (PCB) and is provided to face the upper substrate 11, and the electrode pad 14 is provided at a portion which is opposite to the sensor electrode 13.
The current-carrying member 15 is provided between the sensor electrode 13 and the electrode pad 14, and as a compressive coil spring, the current-carrying member 15 becomes elastic to the sensor electrode 13 and the electrode pad 14, and is electrically connected to the sensor electrode 13 and the electrode pad 14, respectively.
As such, the touch switch 10 is configured such that when the upper substrate 11 comes into contact with a user's finger, a variation in capacitance is transmitted to the capacitance sensing circuit 16 through the sensor electrode 13, the current-carrying member 15 and the electrode pad 14 according to the variation in composite capacitance of the upper substrate 11 made of non-conductive materials and capacitance of the human body, thereby enabling the human body's touch to be sensitively sensed.
However, as described above, the conventional switch 10 is problematic in that a variation in capacitance between the sensor electrode 13 and the electrode pad 14 is not sensed when the current-carrying member 15 composed of the compressive coil spring loses buffer power.
Also, it is problematic in that the current-carrying member 15 provided at both ends based on an illustrated direction is a shorter life span because a difference in buffer power between the current-carrying member 15 provided at both ends and another current-carrying member 15 provided in a center portion based on the illustrated direction occurs.
Also, as described above, it is problematic in that a variation in capacitance is not accurately transmitted to the capacitance sensing circuit 16 due to the difference in buffer power.